Several dyes that absorb and emit light in the visible and near-infrared region of the electromagnetic spectrum are currently being used for various biomedical applications due to their biocompatibility, high molar absorptivity, or high fluorescence quantum yields. This high sensitivity parallels that of nuclear medicine and permits visualization of organs and tissues without the negative effect of ionizing radiation. Most dyes lack specificity for particular organs or tissues and, hence, these dyes must be attached to bioactive carriers such as proteins, peptides, carbohydrates, and the like to deliver the dyes to specific regions in the body. Several studies on the use of near infrared dyes and dye-biomolecule conjugates have been published (Patonay et al.,1991; Slavik, 1994 Brinkley, 1993; Lee and Woo, U.S. Pat. No. 5,453,505; Hohenschuh, WO 98/48846; Turner et al., WO 98/22146; Licha et al., WO 96/17628; and Snow et al., WO 98/48838). Of particular interest is the targeting of tumor cells with antibodies or other large protein carriers as delivery vehicles (Becker, et al., 1999). Such an approach has been widely used in nuclear medicine applications, and the major advantage is the retention of a carrier's tissue specificity since the molecular volume of the dye is substantially smaller than the carrier. However, this approach does have some serious limitations in that the diffusion of high molecular weight bioconjugates to tumor cells is highly unfavorable, and is further complicated by the net positive pressure in solid tumors (Jain, 1994). Furthermore, many dyes in general, and cyanine dyes, in particular, tend to form aggregates in aqueous media that lead to fluorescence quenching. Therefore, there is a need to prepare low molecular weight dye-biomolecule conjugates to enhance tumor detection, and to prepare novel dye compositions to preserve fluorescence efficiency of dye molecules.
The publications and other materials used herein to support the background of the invention or provide additional details respecting the practice, are incorporated herein by reference, and for convenience are respectively grouped in the appended List of References.